Brazil fans in Sao Paulo's Vila Madalena light fireworks and sing in celebration after the host nation's 3-1 win over Croatia to open the World Cup.

SÃO PAULO — Brazil doesn’t do subtlety, not least during its first World Cup in 64 years. You start your day changing travel plans because the police have fired tear gas and rubber bullets at street protestors. You’re stunned when the express train to the soccer stadium is nicer than any subway you’ve taken in America. And you’re blown away by the extremes of a World Cup opener that gives you so much whiplash you need a neck collar by the end.

What was the most visceral moment on this memorable day? Maybe it was when an entire stadium of Brazilians thundered the second verse of their national anthem a cappella. Or when Brazil’s Marcelo silenced the crowd by knocking the ball into his own net just 11 minutes in, the most horrible start anyone in Brazil could have imagined. Or perhaps it was when Neymar fired home the go-ahead penalty and the fans erupted in joy, only to see president Dilma Rousseff on the Jumbotron and change their chants to: “HEY, PRESIDENT, SHOVE IT UP YOUR ---!”

You knew we were in for a wild day when several banks of floodlights in the new $400 million Arena de São Paulo went out right after kickoff. Brazil isn’t ready was the ominous message, and the team itself looked as much in the early going. Croatia was creating more chances, displaying the absolute nerve to play Brazil toe-to-toe with three attacking central midfielders. Several of the Brazilian players looked tentative at the start, but then things changed as those lights came back on.

A goal from Neymar, Brazil’s star, placed perfectly off the post and in. A second Neymar goal, this one from the spot after a soft penalty and some of the worst embellishment (by Fred) that you’ll ever see. And then the coup de grace, a toe-poke on the break by Oscar, the best player on the field all game.

Maybe Brazil was ready after all.

Or maybe not. Just when you think you’re figuring out this country, it throws you a surprise. Thursday’s game will raise questions over whether Brazil really should be the favorite to win the World Cup, especially with a shaky defense. But the canary yellow symbol of Brazil—this country’s greatest brand—may just be the embodiment of a nation that’s far more complex than the Girl of Ipanema.

Brazilians really do love soccer in the spiritual home of the sport, and yet so many are angry over the World Cup, the way FIFA has essentially occupied the state. The mood in São Paulo this week was strangely subdued, as though you couldn’t tell a World Cup was about to start, and yet the passion for Brazil was overflowing on gameday at train stations, on the streets and, of course, in the stadium itself.

But even then there was an element of uncertainty. What should have been a remarkable human moment during the opening ceremony—a paraplegic using a mind-controlled exoskeleton to walk upright and deliver the first kick—was buried so badly by FIFA that almost nobody in the stadium or on TV knew it had happened. (Too bad. The Brazilian neuroscientist who designed the device deserves a Nobel Prize.)

And for a country that has won five World Cups, there sure seems to be a lot of self-doubt in Brazil about its soccer team. Maybe it’s the memory of the last World Cup here, in 1950, when Brazil lost to Uruguay in the final game after everyone was expecting a World Cup title. You got the feeling after Marcelo’s own-goal that the self-doubt was creeping back in, that maybe Brazil coach Luiz Felipe Scolari was all bully bluster when he guaranteed a World Cup title not long ago.

Yet there are moments when you see the possibilities of Brazil, when Neymar knifes through the Croatian defense, when Oscar surges into space, that you can envision Brazil raising the trophy 31 days from now.

The promise of this country is off the charts, whether you’re talking about the national team or the economy or the young people who want to do things a different way from their elders. I’ll have two lasting images from this opening World Cup day: One will be closing my eyes and listening to 60,000 Brazilians belt out their national anthem like a church hymn.

The other will be the little Brazilian girl who was perched on her father’s shoulders next to me as they walked to the stadium. She was gazing in amazement at the whole scene of humanity, taking it all in, and I couldn’t help but wonder how she’ll remember the experience someday. In the end, I was struck by two things: She had no idea what was coming next, yet she still looked supremely confident moving forward into the unknown.

We have a lot to figure out still about Brazil, the team and the country. They don’t do subtlety here, after all. But I want to know more. Good thing we’ll be here for the next month.